Tire tread

ABSTRACT

A pneumatic tire is provided with a tread having a traction pattern consisting of grooves and sipes. The tread pattern inhibits stone retention within the tread by suspending or cradling the stone spatially from the bottom of the groove or sipe. The grooves are provided with transverse crossbars or buttresses having a configuration and dimension relative to the groove to support or cradle a stone above the bottom of the groove. The sipe, or traction-slit, is arranged with parallel side walls wherein a first portion extends from the tread surface radially inwardly, and a second portion is formed from segments extending from the first portion but diverted or angled to alternate sides of the mid-plane extending from the first portion. The segmented sections are provided in several forms which are either twisted, angled, turned or crimped for misalignment relative to the upper or first portion of the sipe.

United States Patent Hoke" 1451 Dec. 19, 1972 [54] TIRE TREAD [72]Inventor: Gilbert .1. Hoke, Kenmore, N.Y.

[73] Assignee: Dunlop Tire and Rubber Corporation, Buffalo, NY.

22 Filed: Oct. 12,1970

[21] Appl. No.: 80,139

Related us. Application Data [62] Division Of SCI. No. 750,387, June 27,1968, abandoned.

[52] US. Cl ..l52/209 [51] Int. Cl ..B60c 11/06 [58] Field of Search..152/209, DIG. 604

[56] References Cited UNITED STATES PATENTS 3,055,410 10/1962 Caulkins..'.l52/209 2,843,172 7/1958 Berryetal ..l52/2()9 2,268,344 12/1941Shesterkin ..l52/D1G. 604

Primary Examiner-James B. Marbert Att0rneyRauber & Lazar [57] ABSTRACT Apneumatic tire is provided with a tread having a traction patternconsisting of grooves and sipes. The tread pattern inhibits stoneretention within the tread by suspending or cradling the stone spatiallyfrom the bottom of the groove or sipe. The grooves are provided withtransverse crossbars or buttresses having a configuration and dimensionrelative to the groove to support or cradle 21 stone above the bottom ofthe groove.

The sipe, or traction-slit, is arranged with parallel side walls whereina first portion extends from the tread surface radially inwardly, and asecond portion is formed from segments extending from the first portionbut diverted or angled to alternate sides of the midplane extending fromthe first portion. The segmented sections are provided in several formswhich are either twisted, angled, turned or crimped for misalignmentrelative to the upper or first portion of the sipe.

4 Claims, 22 Drawing Figures PATENTED m w 1972 saw 1 or av INVENTOR.6/:(5R7 a: HONE- 3 ,4 rmpwm PATENTEEP 19 I97? 3. 7 06,334

sum 2 or 3 INVENTOR. GMBERT J. HOKE BY wgxg 611s Arramvn's TIRE TREADThis is a division of application Ser. No. 750,387, filed June 27, 1968now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to pneumatic tires and in particular to the traction pattern ofthe tire tread wherein the grooves and sipes are arranged to minimizestone pick-up and stone retention.

2. Description of the Prior Art The rubber treads of pneumatic tires arecommonly provided with a plurality of transversely spacedcircumferentially continuous, relatively narrow, anti-skid grooves toincrease the traction properties and flexibility of the treads. Suchgrooves are commonly made circumferentially straight or of a tortuousshape, i.e., zigzag, sinuous, etc.

The grooves of a tortuous shape are considered preferable for such ashape because such a shape provides a much greater groove edge effectivefor increasing the traction and anti-skid properties of the tread, andalso presents the groove edges in various directions so as to increasethe traction and anti-skid properties in all directions.

The rubber treads are also now customarily provided with slit-likegrooves r traction-slits, more commonly called sipes, between thegrooves and in the load-bearing ribs of the tire. The sipes increase theedge areas of the load-bearing portions and thereby improve the tractionand other desirable characteristics of the tread pattern.

Thus, during wet-pavement conditions, sipes also function to dissipatewater from the area of tire contact with the road thereby drying theroad surface, producing a better gripping of the tread on the surface.

The portions of the siping below the surface of the tread are usually inthe same plane and in alignment with the siping on the tread surface asseen by the viewer, i.e., the slot configuration of the pattern on thetread surface itself is identical with the slot configuration or patternbelow the surface of the tread. The maximum depth of the siping that isdesirable is provided for adequate road gripping so that throughout thewearing down or erosion of the tread the siping is maintained.

Certain problems occur with the siping heretofore used in certain tires,particularly when the siping was relatively deep extending inwardly ofthe tire tread towards the carcass upon which the tread is formed. Thisdeep siping allows for foreign objects, especially stones, to enter intothe siping openings in the tread surface early in the tires life. Due tothe narrowness and depth of the siping slots, the stones are held ortrapped within the siping by the compression from the rubber on thesides or walls of the siping. Eventually these foreign objects areforced downwardly and finally against the bottom or base of the slots bythe repeated pumping forces developed by the tire during its use. As thetire is subjected to use and wear, the foreign objects are subjected toadditional forces or pressures as the thickness of the tire tread rubberdecreases. Furthermore. additional foreign objects or stones may betrapped above the original object thereby exerting an additional inwardpressure on the first or most inward foreign object. Such foreignobjects having sharp edges or points cause rapid cutting and tearing ofthe side walls and bottom of the siping and penetrate the under treadrubber and damage or sever the tire cords of the carcass. Such damagecauses premature tire failure of otherwise renders the tire unfit forrecapping or retreading.

The problems with respect to the large grooves, more particularly,permit the foreign objects, such as stones, to enter into the grooveearly in the tires life. The depth of the deep grooves allows the stonesto be held or trapped by the compression of the rubber in the sides orwalls of the ribs formed by adjacent grooves. Eventually the stones areforced against the bottom of the groove by pressure of the load on thetire and road surfaces. As the tire wears the stone is subjected toadditional pressure as the depth of the tread rubber decreases oranother stone may be trapped above the original one exerting pressure onthe first stone. If the lodged stone has a point or sharp edge, thepressure may cause the stone to cut through or split the bottom of thegroove to penetrate the under treaded rubber and the cords of the tirescarcass.

The grooves or sipes, or both, however, thus, have occasioned annoyanceand damage as the result of picking up or holding stones and other hardobjects of various sizes and dimensions. Problems relating to both thegrooves and sipes still remain notwithstanding the many designs ofgrooves heretofore proposed.

It is the general object of this invention, therefore, to improve thetraction pattern of pneumatic tires with respect to the stone rejectionproperties of the grooves and sipes.

SUMMARY OF THE INVENTION According to the invention there is provided apneumatic vehicle tire having a traction-pattern in the tire treadprovided with grooves or sipes generally extending radially inwardlyfrom the surface of the tire tread.

The grooves are provided with crossbars extending transversely acrossthe bottom portion of the groove. The crossbars may be horizontal orparallel with respect to'the tread surface merging with orperpendicularly into the side walls of the grooves, The crossbars mayalso extend upwardly forming buttresses against the side walls of thegrooves as a crescentshaped crossbar merginggradually or tapering intothe side wall spatially below, i.e., radially inwardly, of the treadsurface. Furthermore, the crossbar may extend along the side wall of thegroove to the tread surface forming -in profile a U-shaped crossbar,preferably with the upper portions slightly tapered. The cross sectionof the crossbars may be in rectangular, curved or triangular form. Thespacing between the crossbars is equal or less than the width of thecrossbars.

Foreign objects of significant size, such as stones, that may penetratethe groove are suspended within the groove by being cradled by one ormore adjacent crossbars, This suspension prevents the stone frompenetrating deeper into the groove and eventually damaging the base ofthe groove by cracking the bottom or corners thereof or tearing furtherinto the tread rubber eventually tearing or rupturing the carcasscomprising the cords thereof. Such damage causes premature tire failure,such as blow-outs, or otherwise renders the tire unfit for recapping orretreading.

According to the invention further, the sipes are arranged in aconventional manner with parallel side walls extending inwardly from thetread surface to a desired depth. The 'parallel walls are then extendedin segmented configuration, and each segment may be angled from themid-plane of the upper portion of the sipe respectively to alternatesides of the plane extended from the sipe mid-plane. Alternatively, thesegmented portions may be turned, twisted or crimped to establish apattern that is, in effect, in misalignment, with respect to the uppertread portion defined by the upper sipe. Foreign objects, such as stonesof size that penetrated into the sipe are cradled or suspended withinthe sipe above the lower segmented portions by the crotch of the sipe.

BRIEF DESCRIPTION OF THE DRAWINGS I The nature of the invention ishereinafter further explained in greater detail with reference to theaccompanying drawings, forming a part of this application in which:

FIG. 1 is a perspective view, partly in section, of a pneumatic tireprovided with a tread pattern according to the invention, having eitheror both the grooves and sipes;

FIG. 2 is a plan view of a portion of a groove according to theinvention;

FIG. 3 is a sectional view of the groove taken on the section indicatingline 3-3 of FIG. 2;

FIG. 4 is a sectional view of the groove taken on the section indicatingline 4-'4 of FIG. 2;

FIGS. 5 and 6 are sectional views of the groove similar to FIG. 3showing a modification of the crossbars in the grooves;

. FIGS. 7 and 8 are sectional views similar to FIG. 4 showing otherformsofcrossbars in the grooves;

FIG. 9 is a plan view of the groove showing another example of the tiregroove of the invention wherein the crossbars are arranged in analternate configuration, buttressing the respective opposing walls ofthe groove;

FIG. 10 is a sectional view of the groove taken on sectional line l0-l0of FIG. 9;

FIGS. 11 and 12 are sectional views similar to FIG. 10 showing alternateforms of the crossbars in the tire groove;

FIG. 13 is a plan view of One form of sipe according to the inventionshown disposed in the rib formed by adjacent grooves;

FIG. 14 is a sectional view of the sipe taken on the section indicatingline l4l4 of FIG. 16;

FIG. 15 is a view similar to FIG. 14 showing an alternative formthereof;

FIG. 16 is a sectional view of the sipe taken on the section indicatingline l6-l6 of FIG. 13;

FIGS. 17 and 18 show in section similar to FIG. 16 other forms of sipesaccording to the invention;

FIG. 19 and similar but fragmentary portions thereof, FIGS. 20, 21 and22, show other forms of sipes according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings andin particular to FIG. 1, there is shown a section of a pneumatic tireincorporating in the rubber tread 10 thereof several anti-skid grooves16 and several sipes 20 formed in accordance with the present invention.While only several grooves and sipes are shown, it will be appreciatedthat as many sipes or grooves or both as may be desired may be provided.

The tire illustrated is otherwise of conventional construction andincludes in addition to the rubber tread l0, rubber side walls 14, afabric carcass l2 and annular bead wire bundles 13 to which the carcassis anchored during molding andvulcanizing of the tire. The tire may befabricated and molded in a conventional manner and the anti-skid grooves16 and sipes 20 are preferably formed in the tread 10 during moldingthereof. The term rubber is used to denote natural rubber, syntheticrubber and blends thereof.

The groove 16, according to the invention, is provided with a pluralityofcrossbars 18 as shown in FIGS. 2, 3 and 4. The crossbars arepreferably integrally formed from the bottom of the groove 16 andextend, across the groove from one side wall to the other. The crossbar18a of FIGS. 3 and 4 is of the form that is I generally parallel withthe tread-surface 11. The width W (FIG. 4) or thickness of the crossbarsmay be varied as desired with relation to the height H (FIG. 3) of thecrossbar above the bottom of the groove. Various combinations of thewidth (W) to depth (H) ratio can be used depending upon the groove width(G) and depth (D, FIG. 3) used. The spacing S (FIG. 2) between thecrossbars 18 should be such as to assure the suspension of the stones orother foreign objects that may penetrate the groove and be retainedtherein. The stone is thereby cradled above the bottom of the groove byone or more of the crossbars.

According to the invention, the spacing 19 having a dimension S (FIG. 2)between the crossbars 18 should be not more than and preferably lessthan the width G (FIG. 3) of the groove. The width W of the crossbarwill be selected in relation to its height H, and these dimensionsrelative to the groove width (G) and depth (D) are determined inaccordance with design requirements as will be apparent and understoodby those skilled in thisart.

In general, the width W of the crossbar will approximate the dimensionof the particle desired to be cradled from the bottom of the groove. Thespacing S will be less than the width W and the height H will be such asto provide sufficient structural support of the particle to prevent itfrom cutting into or otherwise damaging the bottom of the groove.Considering the properties of the rubber usually usedin this art, theheight H (FIG. 3) should be no less than 1/32 inches and may be greaterdepending upon the degree of protection desired.

A stone 24, shown in dotted lines in FIGS. 3 and 4, which may havepenetrated or been forced into the groove 16 and retained therein isshown suspended or cradled from the bottom of the groove by the severalcrossbars 18a. The dotted lines portions in the tread 10 indicate theform of the groove and the crossbar owing to the presence of the stone.Although the position of the stone 24 may be only temporary. sincefurther movement of the tire over the road bed eventually causes thestone to be ejected, it will be appreciated that the stone 24 can besuspended or cradled in that position without being ejected and yet willnot harm the bottom of the groove.

I060ll 0018 The cross-sectional form of the crossbars 18 may be any ofseveral configurations, such as the rectangular form shown in FIG. 4,the semi-circular or curved form shown in FIG. 7, as well as thetriangular form shown in FIG. 8.

A modification of the crossbars of the invention is shown in profile inFIG. 5, in a view otherwise similar to FIG. 3. The crossbars, for thisform indicated as 18b, are crescent-shaped disposed, as a rib, laterallyacross the bottom of the groove and extending radially outwardly fromthe bottom of the groove and against both side walls serving in effectas buttresses thereof and terminating at the side walls at a place belowthe tread surface 10. Such buttresses may also be arranged to terminateat the surface of the tread which surface may extend inwardly of thegroove. Also, the crossbar may be a full rib extending throughout thewalls of the groove, terminating at the tread surface and having auniform height and width. Such a form (18c) is shown in FIG. 6. Thedotted lines indicate a taper of the upper portion of the crossbar thatmay be provided. Such forms of crossbars provide V-shaped or U-shapedcradles or suspension structure for stones which prevents thereby deeperpenetration of the stone and which eventually may effect rejection ofthe stone radially outward from the groove. It should be especiallynoted, as above indicated, that the stone need not be ejected from thegroove. Indeed, the stone may be retained in position, cradledharmlessly from the bottom of the groove, throughout the life of thetire by the crossbar and the side walls of the groove.

It will be appreciated that the crossbars according to the inventioneffectively extend the useful depth of a groove which depth wouldotherwise be prohibitive if, for example, the remaining tread rubber tothe carcass were critically thin. Groove channel depth of the nonskidtype can thus be made to more desirable depths than heretofore forlonger-life-traction requirements and yet obviate the damage caused bystones.

Referring now to FIGS. 9 through 11, there is shown other forms ofcrossbars according to the invention shaped as buttresses disposedalternately respectively to opposite walls along the longitudinaldirection of the groove. The crossbars 26a and 26b extend from one lowerside wall portion of the groove 16 laterally across the groove and slopeupwardly into the opposite .wall, merging therein at a locationspatially radially inwardly from the tread surface 11. The upper surface27 of the crossbars 26a and 261; may be curved outwardly in profile asshown in FIG. 10 or may be linear 29 as shown in FIG. 11 for thecrossbars 28a and 28b. The alternating crossbars may also be arranged toextend to tread surface 11 as shown in FIG. I2. The crossbars 30a and30h curve from a lower portion of one side wall of the groove 16upwardly across the groove to the plane of the tread surface and connectto the opposite side wall by a flat portion 31. The cross-sectional formof the crossbars 26, 28 and 30 may also be shaped as shown in FIGS. 4, 7and 8 as described above with respect to the crossbars of FIGS. 3, 5 and6.

Referring now to FIGS. 13 through 22, there are shown sipes according toanother feature of this invention. The sipe or traction-slit 20 isformed or cut into the crown of the tread of the tire in the rib portionthereof formed between adjacent grooves. The grooves may be ofconventional form or in accordance with the form 16 of the presentinvention as described herein above.

The slots of the sipe may extend into the tread any desired depth butusually approximating 25 to percent of the total thickness or depth ofthe tire tread 10. Also, it is the usual practice to form the walls ofthe sipe so as to be parallel. It will be understood, however, that thesipe may extend into the tread at angles approaching 15 from the radialplane of the tire and the sipe of this invention may be used in suchconfigurations. Further, it has been the usual practice to extendcertain alternate portions of a sipe deeper than intermediate portionsin order to strengthen and support surrounding rubber tread elements.Thus, tearing and chunking out rubber elements adjacent the sipe by thestress or strain on the sipes owing to high centrifugal forces or highacceleration in braking forces are prevented. Nevertheless such forms ofsipe allow for entrapment and deep penetration of stones which becomeembedded in the sipe to be eventually forced inwardly through the bottomof the sipe tearing it and thereafter cutting into the carcass of thetire. According to the invention, this problem is solved and the stonesare inhibited or virtually prevented from deep penetration into thetread.

Referring to FIG. 1, the upper portion 21 of the sipe 20 is formed in aconventional manner. The lower portion 22 is formed in accordance withone embodiment of the invention by segmenting the sipe-forming elementand angling or diverting the segmented elements radially inwardly fromthe plane of the upper sipe to alternate positions about the radiallyinwardly extended mid-plane of the upper sipe portion 21.

Referring particularly to FIGS. 13, 14 and 16, a sipe 20 is shown formedin the rib 23 between grooves 16. Segmented portions 42 and 44 aredisposed or angled on opposite sides of the mid-plane formed by theextension of the upper sipe portion 21. The sipe segments 42 and 44,etc., are generally rectangular in elevation. A stone 24 is shownsuspended in the upper portion of the sipe 21 on adjacent segmentedportions and the crotch 43 formed at the junctions of the adjacentsegmented portions. The stone is thereby prevented from furtherpenetration into the lower sipe portion 22 owing to such cradle actionand also to the walls of the sipe serving as a restriction by the abruptchange in direction of the lower sipe wall portion relative to the uppersipe wall portion. Further stone penetration is prevented as well by thedimension of a given segment 42, 44, etc., being smaller than any stoneof significant size which may have penetrated the sipe.

The segmented legs 42 and 44 may be angularly diverted as shown, forexample, in FIG. 17 wherein the segments 42 and 44, in end-view, aredog-legged from the upper portion 21. FIG. 18 shows a dog-leg of asharper angle.

It should be noted, with respect both to sipes, as well as the groovesaccording to the invention, that stones or other foreign objects ofsignificant size are potentially harmful when their size approaches orapproxi mates the width dimension of the groove or sipe. Thus, verysmall stones relative to the opening of the groove will be of no seriousconsequence or problem with respect to cutting the bottom of the grooveas they cannot be retained by the side walls of the groove.

Likewise, large stones cannot penetrate the sipes, and fine stones ofdimensions much less than a sipe are not a problem since the sipe wouldnot, in general, retain or entrap such fine particles. It is thus to beunderstood that the stones that are prevented from retention orentrapment by the grooves and sipes of this invention are of significantsize relative to the dimension of the groove or sipe.

FIG. is another form of angled segmented sipe similar to that of FIG. 14wherein the lower portions 42a and 44a are triangular in elevation.

In general, according to the invention, various configurations of sipebelow the upper portion 21 may be provided by turning, twisting orcrimping the sipeforming segmented elements to form the sipe portions50, 52, etc., or angling such sipe-forming elements alternately onopposite sides of the mid-plane of the extension of the upper sipe. Forexample, referring to FIG. 19, a plan view of a sipe is shown with thesubsurface sipe-element 50 and 52 twisted so that one edge 54 of theelement 50 is disposed on one side of the sipe mid-plane 20 and theother edge 56, of the same segmented element 50 is disposed on theopposite side of the mid-plane of the sipe 20. The junction 58 of theadjacent segmented portions forms a crotch serving to support a cradledstone as described previously herein.

Another form of lower sipe-segment is shown in fragmentary plan viewFIG. 20, showing elements 50a, 52a, etc., formed into an S-shape whereinthe end portions 54a and 56a of each segment are disposed in therespective positions as shown.

Still another form of lower sipe-segment is shown in FIG. 21 whereinsegmented elements 50b, 5212, etc. are crimped, being generally U-shapedin cross-section. FIG. 22 shows similar crimping of elements 50c and 520but in symmetrical alternating arrangement.

It will now be appreciated that the sipes and grooves according to theinvention serve to inhibit, if not substantially prevent, the retentionof foreign objects, such as stones that may be picked up and theconsequent penetration of such objects deep into the tire tread tofracture the tread or otherwise damage the carcass.

Any stones that are retained in the groove or sipe are cradledharmlessly from the bottom thereof. Furthermore, as the tread surfacewears, the crossbars and subsurface sipes will serve as additiontraction edges to thereby prolong more effectively the traction-life ofthe tire.

Although several preferred forms of the invention have been described,it will be apparent that modifications may be made therein by thoseskilled in the art without departing from the scope of the invention asset forth in the appended claims. It should, thus, be understood thateither the sipes, alone, or the grooves, alone, may be used incombination respectively with conventional tire treads otherwise nothaving the features as herein described and claimed respecting the stonerejecting features.

What is claimed is:

l. A tire comprising a tread provided with a plurality of groovesforming between them a plurality of loadbearing ribs and a plurality ofsipes in said ribs, said sipes each having walls substantially parallelto each other, said sipes further comprising a first portion extendinradially inwardly from the rib surface and a secon portion comprisingsegments extending radially inwardly from the first portion, thelongitudinal plane of at least the part of each of the segments adjacentto the first portion being disposed at an angle to the longitudinalplane of the first portion and at least a portion of the segments ofsaid second portion lying alternately on one side of the longitudinalplane of the first portion and then on the other side.

2. The tread according to claim 1 wherein each segment is twistedwhereby its surface is a warped plane generated by an angular rotationof the plane along the longitudinal axis of the segment.

3. The tread according to claim 1 wherein each segment is bent at leastonce about an axis parallel to the tread surface.

4. The tread according to claim 1 wherein each segment is crimpedwhereby the contour of said segment is generally U-shaped incross-section.

lOl l 0020

1. A tire comprising a tread provided with a plurality of groovesforming between them a plurality of load-bearing ribs and a plurality ofsipes in said ribs, said sipes each having walls substantially parallelto each other, said sipes further comprising a first portion extendingradially inwardly from the rib surface and a second portion comprisingsegments extending radially inwardly from the first portion, thelongitudinal plane of at least the part of each of the segments adjacentto the first portion being disposed at an angle to the longitudinalplane of the first portion and at least a portion of the segments ofsaid second portion lying alternately on one side of the longitudinalplane of the first portion and then on the other side.
 2. The treadaccording to claim 1 wherein each segment is twisted whereby its surfaceis a warped plane generated by an angular rotation of the plane alongthe longitudinal axis of the segment.
 3. The tread according to claim 1wherein each segment is bent at least once about an axis parallel to thetread surface.
 4. The tread according to claim 1 wherein each segment iscrimped whereby the contour of said segment is generally U-shaped incross-section.